<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>弧形边框css</title>
</head>
<body>
    <div class="tab"></div>

    <style>
        .tab{
            margin: 0 auto;
            width: 150px;
            height: 40px;
            background-color: #ed6a5e;
            border-radius: 10px 10px 0 0;
            position: relative;
            transform: perspective(30px) rotateX(20deg);
            transform-origin: center bottom;/* 旋转原点在这儿 */
        }

        .tab::before, .tab::after{
            content: '';
            position: absolute;
            height: 10px;
            width: 10px;
            bottom: 0;
            background: #ed6a5e;
        }
        .tab::before{
            left: -10px;
            background: radial-gradient(circle at 0 0, transparent 10px, #ed6a5e 10px);
        }
        .tab::after{
            right: -10px;
            /* 可写10px 或者 100% background: radial-gradient(circle at 10px 0, transparent 10px, #ed6a5e 10px); */
            background: radial-gradient(circle at 100% 0, transparent 10px, #ed6a5e 10px);
        }

        /* 弧形边框 */
        .tab::before{
        }
        .tab::after{
        }
    </style>
</body>
</html>